Production of pentaerythritol



, Patented Sept.` 30, 19.52 y

'A 'i' Y lCorpus Christifllex., assig-norsto.CelanesesCorf l porationrof'America, a,corporationof'Delaware` Nofnr'awmg, Application March ze, 1949,

Serial' N0. 83,766

f i V1 l Thisinvention; relates to 'a' 'process-for the production'of pentaerythritol vArrobject of this invention is the provision of an improved process for the production o'fpentav"erytlir'tol by reacting formaldehyde' and acetaldehyde wherein ythe formationv of Vexcessive [amounts )of 'dipentaerythritol'f and polypentaerythrfrtoljmaylde 'avo i ded.

6 Claims. (Cl. 26o-e635.)

41other'loic-3eatsl 'ofjthis intention v will appear liront-the following-detailed description. L

The vapor'pha's'e `partial oxidation of aliphatic hydrocarbons, s'ucli'as propane, butane or mix- 'tures'f' thereof, employing'j' airor oxygen as" the xidizingjagent, yields a `complex"mixture of products-'fincludin'g"formaldehyde, 'acetaldehyde methanol; acetone, methyl'al and :other acetals, methyl ethylketone, tetr'ahydro'furan andI "other 'comptantds".`r The oxidation iseffected bymixin'g" butane for' propane with apredetermined amountfof-lair'for Oxygen;l heating 'th-'e' mixture-'5to 'reaction `v temperatur, allowing the resulting 'exth'ermic oxidation 'reaction to proceedto =th`e desired Idegree YandthenY halting the reaction-by quenching the h ot reaction gases with coolwater. 'If'l'ieformaldehyde -present'in the hot reaction gasesfisabsorbe'ddn thef'quench Water and the latter-is-then puri'edto yieldV aqueous formal- `dehyde-*solutions 'off the ldesired' concentration `rv'vhichinay beemployed satisfactorily `as an in'- terme'diate-'for-'any of 'the widely'diversiied co1n- "rnercial reactions which utilize formaldehyde] AOnefof said'reactins involves the formation' of"pentaerythritol'bythe exothermic reactionoi ai mixtureV` of formaldehyde and acetal'dehyde in an aqueous# alkaline medium and is well known.

aiplurality -of stages, the reaction beinginitiated atA -arelatively llow temperature and` then com- "pletedby effectingv a secondary reactionatia-conf' "siiderably higher temperature;V In leiecting*the reaction described one ofthe major problemsjis- 'to avoid the formation of dipentaery'thritol `and hyde-employe'din sai-d reaction preferably jc npolypentaerythritol inl excessive amounts. These 1 higher molecularu weight* reaction product sif :are considered impurities and their presenceji's"usu- AallyJ quite undesirable. I n order` to xeiectf L the desiredAA secondary condensation `Ireaction raire la- 'tivelyhigh 'temperature is usually necessary to 'initiate-it. lrloweverithe use fof'a relatively high V'reaction' temperature 'lis lprone to yieldafpmfecijableamounts of f dipentaerythritol andfpolypentaerythritol.

llflehaye` found, however, ,that ,aqueousjfo m'- ia'ldehyde btained""by the" vapor phase partial `terrinerature f of the reaction mixturev being* alf'- solution obtained by evaporation.

' form ald'ehyde j for each molecular proporti vacetalde'hyde present: andthe aqueous vs luir .18% by weight ci said reaction mixture;

oxidation of hydrocarbons 'beh'avesin ai'v fashion different rfrom commercialEV formaldehydef'proe duced bythe oxidation of? methanohfor: example,

and thatfpentaerythritol may beforr'ned 'very rapidly and 'l in excellent yield from vsaidi'orr'n'al'- dehy'de when reacted with acetaldehydefwith'out the-production ofv excessively hignjamountsa-o'f dipentaerythritol and polype'ntaerythr-itol' f. By employing formaldehyde-obtained by the vapor thefinitial' reaction may he efiect'ed'at aliigl'lertemperature than vheretofore* employedlan-df-'the Lvsecondary .reaction nitiatedfand completedat an I' appreciahly lower temperature. l'ni'accorldfance f with our nov-e1 process, a" mix-ture 'of formf- 1aldehydev obtained'v byv the vapor" phase partial oxidation ol?-A aliphatic` hydrocarbons, andace'tldehyde in suitable molecular proportion isadded to an aqueous slurlyof calcium hydroxide-fand an initial exothermic f reaction takes `pl-"aycei 4'the tureto fall.' 4The reaction mixtureisthenheated tot a temperature-"oil' ahout'Zto 15 Fnablw'efth'e previous temperatfi'rfereached afterf the ternpeta-y ture has fallen` sonas;v toaeffect a second'fex'o'- thermi-c, reaotlon. y"After I naximurn" 'reaction temperature `ris attane d; duringethegsecondary frejaction;l 'the reaction mixture is.` immediately cooled. [The calcium hydroxide present inthe reaction-inixtur`e is then substantially -allnevue tralizerL preferably bythe addition d f sulfuric 'acidto-'thefre'actionmixture, and the' calcium sulfate formedfilteredoff. Thepentaerythritol in solution is separated: by" ,effectingv a", vacuun1 evaporationY ofthe solution, 'andthen rystallizing the,v pentaerythiit'olV ,from the concentrated tainsgfrom 4.5 tof5.5 molecularproporti'o calcium hydroxide tojtvhich'Y it isr addedpre erf- 'ably contains-0.6 yto 0.8 molecular `prnnortiroide of calcium hydroxide. Most advantageously, he

of watenthat the tot-a1 aidehyde comentan til-'e reaction'inixture attent-life addition isf from/14th While we' do ,not wish to be bound yby any theoretical considerations, itis believed that the unique behavior of .aqueous formaldehyde obtained by the vapor phase partial oxidation of aliphatic hydrocarbons in said pentaerythritol formaldehyde from other sources, and this ref..

, 4 ducing the volume of the filtrate obtained after the separation of the initial crystalline precipitate to about half its volume and then cooling to 50?J F. for 4 hours. The crystals are separated from the liquid by centrifuging and are then washed with ice-water. The total yield of pentaegrythritol obtained is about 70fto :75% '.of which only about 5 to.10% comprises dipentaerythritol and polypentaerythritol. The crystals may be `further purified, if desired, by dissolving in hot water, again iiltering to remove any calcium duction in time limits the am-ount of dipentaerythritol and polypentaerythritol formed.

In order further to illustrate our invention, but without being limited thereto, the following example is given:

Example 820 parts by weight molecular proportions) of a 36.7% by weight aqueous solution of formaldehyde, obtained asa.k product ofthe vapor phasepartial oxidation of aliphatic hydrocarbons .such as propane, l'butane or mixtures thereof, are mixed'with 90 parts by weight (2 molecular proportions) :of 98% aqueous acetaldehyde .and the mixtureadded'rapidly to an aqueous slurry of 95.4 parts byweight ofv calcium hydroxide (93% `purity);ini1500 parts by weightof Water. The aldehyde additionv is` completed in 45 minutes. The total aldehyde concentration 'in' the reacytionf-mixture after the addition is completed is about 16% by weight and the temperature about 70 An exothermicreaction takes place and Athe temperature is allowed to rise over the course of. 'about 20 minutes to 107 F., suitable cooling being provided when `the temperature reaches .about-95F. to prevent any excessive rise in temperature-over the desired maximum. vThe reaction mixture is then allowed to stand for y15 .minutes during which time the temperature .dropsto about 98 F. The reactionmixture. is then heated roverthe course of about Vminutes tof107 F. and, afterabout 5 to 15 minutes ,at

ythis `temperature a secondary ;exothermic reaction; takes place-with the temperature rising-t0 a maximum of about 115511.` When maximum temperature is reached,. during the secondary reaction, .the sharp, aldehydic 'odor decreasesl rapidly. After the formaldehyde odor disappears and before anyyellowcolor develops the reaction. mixture is immediately, cooledand -113 parts -by xweight. ofl concentrated sulfuric vacid Vadded .rapidly inthe form of a 50% aqueous solution. Calcium Sulfateprecipitates on addition of the sulfuric acid and is ltered ofi vand washed with about 500 .parts by weight of hot water. The

. vcolorless onpale green ltrate obtained is combined withthe wash water. The combined solution, ..which contains about '7% 'by weight of spentaerythritol, has a pHof about 2.9 and contains 3 to 3.5% by weightof formic acid.

.The solution thus obtained is then evaporated under. a vacuum of 26 to 28 inches of mercury ato' aboutone-quarter of its original volume after which.the concentrated Isolution is chilled at about.,50.F. for` 4 hours. lPentaerythritol crys-y talsare formed on standing and are separated .by-.'centrifugingthe solution and then washing 4the' ...crystals with ice-water. .The filtrate or l.ir'iother liquor contains about 6% by weight of ',.flormic acid while the evaporator distillate obv.tained.contains 2.8% formic acid, about 60% of the formic. acid, .originally presentcom'ing over during the initial vacuum evaporation. A second .cropsiof crystals may .be.readilyy ,obtainedryby resulfate present and then recrystallizing.

The course of the secondary reaction prior to the addition of the sulfuric acid may be followed very conveniently by employing a polarograph. Thus, the gradual decline in the free formaldehyde content may be traced readily and the optimum time for acidification to avoid overcondensation readily determined.

sisting yof lacetaldehyde 'acetaldehyde to an from 0.6.tof0-8`molecular proportions of calcium It is to be understood that the foregoing detailed description is given merely byway of illus-y tration and that many variations maywbeniade therein without departing from the spiritfo'fpur invention.

Having described our invention, .to secure by Letters Patent is:

1. Process for the production of pentaerythritol, which comprises adding a mixture of acetaldefhyde and an aqueous solution'of formaldehyde obtained by the vapor phase partial oxidation of aliphatic hydrocarbons to an -aqueous slurry of calcium hydroxide, allowing the temperature of the reacting mixture during the resulting exo.- thermic reaction to rise to a maximum of about to 115 F., continuing the reaction without further heatingwhile allowing the temperature to fall, heating the reaction mixture. to increase the temperature thereof, above the previous tom perature reached. after the temperature Ehas fallen, by at most 15 F. to initiate a second exofthermic reaction, immediately cooling the reaction mixture after maximum reaction tempera.- ture isattained, and then neutralizing the calciumhydroxide in theA reaction mixture by adding sulfuric acid thereto. i 2. Process for the production of pentaerythritol, which comprises adding a mixture ofacetaldehydev and an aqueous solution of formaldehyde obtained by the vapor phase partial oxidation of aliphatic hydrocarbons to an aqueous .slurry of calcium hydroxide, allowing the temperature of the reacting mixture during the resulting-.exothermic reaction to rise toa maximumofv about further heating while allowing the temperature ,to fall, .heating the reaction mixture to increase the temperature thereof, above the previous temperature reached after the temperaturelghas fallen, by at most 15F. to initiate a secondl exothermic reaction, immediately cooling thereaction mixture after maximum reaction tempera.- iure is attained, neutralizing the eaiciumhydroxi'de `in the reaction mixture by adding sulfuric acid thereto, iiltering the calcium sulfate precipitate formed, and separating pentaerythritol from ythe ltrate.

v3.*Process for the production of pentaerythritol, which comprises adding a mixture conand an aqueoussolution oi'vformaldehyde obtained by the vapor phase par.- tial `oxidation of aliphatic.. hydrocarbons in a vratioA of 4.5 to 5.5 molecular proportions of said formaldehyde for each molecular. proportion of aqueous slurry containing *what we'dsirle hydroxide and sufficient water so that the total aldehydes content after the addition is from 14 to 18% by weight of the reaction mixture formed, allowing the temperature of the reaction mixture during the resulting excthermic reaction to rise to a maximum of about 105 to 115 F., continuing the reaction without further heating for about 15 to 30 minutes while allowing the temperature to fall, heating the reaction mixture and increasing the temperature about 2 to 15 F. above the previous temperature reached after the temperature has fallen and effecting a second excthermic reaction, immediately cooling the reaction mixture after maximum reaction temperature is attained, and then neutralizing the calcium hydroxide in the reaction mixture by adding sulfuric acid thereto.

4. Process for the production of pentaerythritol, which comprises adding a mixture consisting of acetaldehyde and an aqueous solution of formaldehyde obtained by the Vapor phase partial oxidation of aliphatic hydrocarbons in a ratio of 4.5 to 5.5 molecular proportions of said formaldehyde for each molecular proportion of acetaldehyde to an aqueous slurry containing from 0.6 to 0.8 molecular proportions of calcium hydroxide and sufficient water so that the total aldehyde content after the addition is from 14 to 18% by weight of the reaction mixture formed, allowing the temperature of the reaction mixture during the resulting excthermic reaction to rise to a maximum of about 105 to 115 F., continuing the reaction without further heating for about 15 to 30 minutes while allowing the temperature to fall, heating the reaction mixture and increasing the temperature about 2 to 15 F. above the previous temperature reached after the temperature has fallen and effecting a second excthermic reaction, immediately cooling the reaction mixture after maximum reaction temperature is attained, neutralizing the calcium hydroxide in the reaction mixture by adding sulfuric acid thereto, filtering the calcium sulfate precipitate formed, and separating pentaerythritol from the iiltrate.

5. Process for the production of pentaerythritol, which comprises adding a mixture consisting of about one molecular proportion of acetaldehyde and about 5 molecular proportions of an aqueous solution of formaldehyde obtained by the vapor phase partial oxidation of aliphatic hydrocarbons to an aqueous slurry containing about 0.6 to 0.8 molecular proportions of calcium hydroxide and suicient water so that the total aldehyde content after the addition is about 16% by ing the resulting excthermic reaction to rise to a maximum of about 107 F., continuing the reaction without further heating for about '15 minutes while allowing the temperature to fall, heating the reaction mixture to increase the temperature to about 2 to 15 F. above that reached at the end of the temperature fall and effecting va second excthermic reaction, immediately cooling the reaction mixture after maximum reaction temperature is attained and the aldehydes substantially all reacted, neutralizing the calcium hydroxide in the reaction mixture by adding sulfuric acid thereto, filtering the calcium sulfate precipitate formed, and separating pentaerythritol from the filtrate.

6. Process for the production of pentaerythritol, which comprises adding a mixture consisting of about one molecular proportion of acetaldehyde'and about 5 molecular proportions of an aqueous solution of formaldehyde obtained by the Vapor phase partial oxidation of aliphatic hydrocarbons to an aqueous slurry containing 0.8 molecular proportions of calcium hydroxide and suicient water so that the total aldehyde content after the addition is about 16% by weight of the reaction mixture formed, allowing the temperature of the reaction mixture during the resulting excthermic reaction to rise to a maximum of about 107 F., continuing the reaction without further heating for about 15 minutes while allowing the temperature to fall, heating the reaction mixture to increase the temperature to about 107 F. and effecting a second excthermic reaction, immediately cooling the reaction mixture after a maximum reaction temperature of about F. is attained and the aldehydes substantially all reacted, neutralizing the calcium hydroxide in the reaction mixture by adding sulfuric acid thereto, filtering the calcium sulfate precipitate formed, and separating pentaerythritol from the ltrate.

MAX O. ROBESON. SOLON A. BLUNDELL, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2.004,010 Naujoks June 4, 1935 2,333,696 Bludworth Nov. 9, 1943 2,401,749 Burghardt et al. June 11, 1946 

1. PROCESS FOR THE PRODUCTION OF PENTAERYTHRITOL, WHICH COMPRISES ADDING A MIXTURE OF ACETALDEHYDE AND AN AQUEOUS SOLUTION OF FORMALDEHYDE OBTAINED BY THE VAPOR PHASE PARTIAL OXIDATION OF ALIPHATIC HYDROCARBONS TO AN AQUEOUS SLURRY OF CALCIUM HYDROXIDE, ALLOWING THE TEMPERATURE OF THE REACTING MIXTURE DURING THE RESULTING EXOTHERMIC REACTION TO RISE TO A MAXIMUM OF ABOUT 105 TO 115* F., CONTINUING THE REACTION WITHOUT FURTHER HEATING WHILE ALLOWING THE TEMPERATURE TO FALL, HEATING THE REACTION MIXTURE TO INCREASE THE TEMPERATURE THEREOF, ABOVE THE PREVIOUS TEMPERATURE REACHED AFTER THE TEMPERATURE HAS FALLEN, BY AT MOST 15* F. TO INITIATE A SECOND EXOTHERMIC REACTION, IMMEDIATELY COOLING THE REACTION MIXTURE AFTER MAXIMUM REACTION TEMPERATURE IS ATTAINED, AND THEN NEUTRALIZING THE CALCIUM HYDROXIDE IN THE REACTION MIXTURE BY ADDING SULFURIC ACID THERETO. 